Blast furnace salamander charting



Dec. 1, 1959 e. H. CRAIG BLAST FURNACE SALAMANDE'R CHARTING Filed Oct. 17, 1957 United States Patent SALAMANDER CHARTING Hammond, Ind., assignor to In- Chicago, ]]l., a corporation of BLAST FURNACE George Herbert Cra g,

land Steel Company, Delaware This invention relates to blast furnaces. More particularly, this invention is concerned with methods and apparatus for charting a blast furnace salamander.

A blast furnace hearth, in which the ore, coke and limestone are reduced to iron, rests on supporting brickwork about 15-25 feet high and of a diameter commensurate with the hearth diameter. This brickwork in turn ordinarily rests on a concrete foundation. The brickwork may also be circumscribed with concrete for reinforcement. The bottom of the hearth is a circular depression initially. In normal operation of the blast furnace the molten iron formed in the reduction process slowly but continuously erodes the bottom of the hearth so that the basin becomes deeper and deeper. The resulting depression or crater formed in the brickwork is called a salamander.

The size of a salamander cavity will, of course, vary directly with the time a blast furnace has been in operation from when it was built or repaired last as well as the size of the particular furnace. Salamander cavities, generally of inverted cone shape, may reach -20 feet in depth, with a major diameter about the same as the bottom of the hearth, in about 3 to 8 or more years of continuous operation. The depth of a salamander is usually not more than one-half the hearth diameter. Salamanders in general may contain from about 100 to 500 tons of metal or more.

The salamander cavity extent and its formation is presently followed by material balance methods in which the iron cast from the furnace is compared with the amount which should have been recovered from the materials added and blueprints of the erosion pattern of previous salamanders. This method, however, is not sufliciently precise to be reliable and, also, while it may indicate the magnitude of the salamander, it does not indicate its shape and location.

The contour and position of a salamander should desirably be known precisely so that the blast furnace will not be shut down prematurely, to eliminate the possibility of a break-through and to facilitate subsequent tapping of the salamander after the furnace is shut down.

After a blast furnace is shut down the molten iron must be removed from the salamander for otherwise it will solidify and greatly obstruct rebuilding the furnace. Tapping a salamander is a time consuming, specialized job in which extreme care must be exercised The procedure in general involves drilling a tap hole at a predetermined slope through the foundation and into the brickwork. Such a tap hole generally is from about 4 to. 10 feet deep. Obviously, the tapping operation will be easiest if the salamander shape is known because then the tap hole may be located at an optimum location. Furthermore, by knowing the location of the salamander bottom the tap hole may be drilled precisely to that location and the maximum amount of iron removed.

It has now been discovered that the formation and shape of a salamander in a blast furnace may be charted by embedding one or more thermocouples (more ac- 2 curately called resistance-thermometers) in the brickwork which supports the furnace hearth and periodically determining the change in electrical conductivity by the thermocouple and thereby the temperature at the location of the thermocouple. The temperature changes will indicate that brick erosion is progressing to the thermocouple and that the salamander is .accordingly enlarging.

The invention will now be described in conjunction with the attached drawings in which:

Fig. 1 is a schematic view in section'of a blast furnace, and

'Fig. 2 is a wiring diagram showing an arrangement for embedding thermocouples in the supporting brickwork.

The blast furnace 10 of Fig. 1 is of conventional design and has hearth 11 supported by brickwork 12. The brickwork 12 is shown eroded to create salamander cavity 13 The brickwork 12 of refractory material is laid in courses during the initial construction of the blast furnace or during rebuilding. As the brickwork is laid at least one thermocouple is embedded therein at a location where the brickwork can be expected to be eroded into a salamander or to where the heat of the molten metal in a salamander can be expected to penetrate. Electrical conducting wires are run from the thermocouple to the exterior of the furnace where they may be terminated as contact points or run directly into a control board. By connecting the thermocouple leads to a source of electrical energy and placing a galvanometer in the circuit the resistance may be measured. vPeriodic readings will indicate the growth of the salamander by variations in electrical resistance of the thermocouple. In the event the molten iron in the salamander contacts the thermocouple or wire leads, the circuit may become broken or the iron, either molten or solidified, will replace the thermocouple or leads in part. However, any of these events will produce a measurable change in resistance which will give the location of the salamander because the position of the thermocouple in the brickwork is known.

Shown in Fig. 2 is a wiring diagram which may be used to chart the width and depth of a salamander as it develops. The wiring apparatus of this figure may be positioned at predetermined locations in the hearth-support ing brickwork as it is laid. Such a wiring apparatus is advisably positioned horizontally between adjacent courses of brick with several such wiring apparatuses embedded in different strata of the brickwork, such as 1-3 feet apart.

The wiring apparatus is made of concentric rings of a light gauge conductive wire such as Chromel. The wires are of uniform resistance per unit of length and preferably of a resistance different than iron. At various intervals leads of wire, such as a a b e f etc. are joined to each of the concentric rings and run through the brickwork to outside the furnace where they are labeled or otherwise identified. In this way the resistance of segments of the concentric rings may be measured, using, of course, a suitable source of electrical energy and a galvanometer to complete the circuit.

As shown in Fig. 2, leads a and :1 from a segment of the innermost ring are connected to a circuit in which is placed galvanometer 15 and battery 16. After taking the electrical resistance reading at this point the terminals 17 and 18 may be shifted to two other leads such as C1C4; d d and e e As the salamander is formed the individual rings or segments thereof experience a temperature rise first which produces a slight change in conductivity that is apparent when compared to previous readings. By periodic checks in the change of the re sistance of the segments of the concentric rings due to heating from a nearby salamander front or melting of the rings or leads by the molten iron a record of salamander growth and location is obtained.

It will obviously occur to those skilled in the art to connect the thermocouples to a master control board 'so that the readings -may be made periodically with a minimum of effort.

Various changes and modification of the invention can be made and, to the extent that such variations incorporate the spirit of this invention, they are intended to be included within the scope of the appended claims.

What is claimed is:

1. A blast furnace for making iron having at least one thermocouple embedded in the hearth-supporting brickwork at a location where it will be responsive to to temperature variations caused by erosion of the brickwork during the formation of a salamander therein.

2. A blast furnace for making iron having a plurality of thermocouples embedded in the hearth-supporting brickwork at a location where it will be responsive to temperature increases caused by erosion of the brickwork during the formation of a salamander therein.

3. A blast furnace for making iron having a plurality of thermocouples embedded in the hearth-supporting brickwork in spaced-apart horizontal planes, and means for measuring the resistance of said thermocouples periodically.

4. A blast furnace having embedded in the hearthsupporting brickwork in spaced-apart horizontal planes, a plurality of concentric rings of an electrically conductive wire having an electrical resistance responsive to temperature changes and a plurality of lead wires connecting each ring and running to the outside of the furnace, and means attached to said leads for determining the resistance in a selected segment of said rings.

References Cited in the file of this patent UNITED STATES PATENTS 2,695,219 Upham Nov. 23, 1954 

